The disclosure of Japanese Patent Application No. HEI 10-342489 filed on Dec. 2, 1998 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
This invention relates to a fuel cell system, more particularly, to a fuel cell system with improved startability.
2. Description of Related Art
In a system relying on fuel cells for the generation of electrical power, the amount of electric power consumed by the load is not always constant. When the fuel cells are designed based on the maximum required power of the load, a high power generation efficiency of the fuel cells cannot be obtained. If the performance of the fuel cells is determined based on maximum power required by a load, it is difficult to maintain high power generation efficiency when the required power drops.
It has been considered to divide the power generating portion of a fuel cell into a plurality of portions and to control each portion based on the required power of the load. For example, Japanese Patent Laid-Open Application No. HEI 04-262370 discloses such technology.
At the time of starting a fuel cell, it is preferable to warm-up the fuel cell so that its temperature is increased to the operational temperature in a short time. To warm up for hours may produce undesirable results. For example, in case of using a reformed gas as the fuel gas, carbon monoxide contained in the reformed gas may poison the electrodes in the fuel cell. However, the related art does not disclose how to increase the temperature of the fuel cell up to the operational temperature at the time of starting.
Accordingly, it is an object of this invention to provide a fuel cell system which can reduce the warm up time for the fuel cells in the system and can operate the fuel cells stability in a shorter time.
In order to achieve this and other objects, the fuel cell has a plurality of power generator portions. A fluid flow passage connected to the power generator portions is changed so that circulating water flows in just part of the generator when the temperature of the fuel cell is not higher than the predetermined value. Accordingly, since the heat capacity of a portion where the fluid flows can be reduced, the temperature of the fluid is raised easily. Thus it is possible to warm up the fuel cell in a shorter time.
In accordance with one aspect of this invention, there is provided a fuel cell system having a plurality of power generator portions. A fluid flow passage is connected to the plurality of power generator portions so as to selectively supply a heating or cooling fluid to selected ones of said plurality of power generator portions. At least one switching device is associated with the fluid flow passage so as to switch the fluid flow passages to supply heating or cooling fluid to at least one of said plurality of power generator portions.
According to this aspect of the invention, a passage controller may be operatively connected to the at least one switching device and is configured to cause the at least one switching device to switch the fluid flow passage based on the temperature of the fuel cell.
According to another aspect of the invention, a fuel cell system comprises a fuel cell having a plurality of power generator portions; a fuel gas passage connected to selectively supply fuel gas to the power generator portions of said fuel cell; at least one switching device associated with the fuel gas passage so as to switch the fuel gas flow to at least one of said plurality of power generator portions.
According to this aspect of the invention, a gas passage controller may be operatively connected to the at least one switching device and configured to cause the at least one switching device to switch the fuel gas passage to a configuration such that the plurality of power generators will generate a maximum heat output, as compared to other switched configurations of the gas passage, based on the temperature of the fuel cell.